A106332 - OEIS

A106332

Decimal expansion of the constant x that satisfies: 1 = Sum_{n>=1} x^(n*(n+1)/2).

6, 4, 5, 2, 2, 2, 7, 0, 3, 2, 3, 6, 0, 2, 0, 9, 7, 9, 1, 3, 4, 2, 5, 1, 6, 6, 3, 9, 4, 4, 0, 2, 6, 3, 3, 2, 2, 5, 4, 7, 2, 7, 4, 4, 3, 6, 4, 0, 5, 7, 1, 2, 2, 1, 0, 7, 4, 2, 2, 0, 1, 8, 3, 9, 0, 1, 3, 6, 5, 4, 6, 7, 1, 5, 7, 3, 9, 6, 4, 9, 9, 7, 2, 0, 1, 4, 4, 6, 9, 3, 6, 9, 3, 5, 0, 0, 2, 6, 6, 1, 3, 4, 5, 5, 1

(list; constant; graph; refs; listen; history; text; internal format)

OFFSET

0,1

COMMENTS

Equals the radius of convergence of the g.f. of A023361 (number of compositions into sums of triangular numbers).

LINKS

Table of n, a(n) for n=0..104.

EXAMPLE

1 = x + x^3 + x^6 + x^10 + x^15 + x^21 + x^28 + x^36 + ...

x = 0.6452227032360209791342516639440263322547274436405712210742201839013654671

MATHEMATICA

x /. FindRoot[ EllipticTheta[2, 0, Sqrt[x]] == 4*x^(1/8), {x, 1/2}, WorkingPrecision -> 110] // RealDigits[#, 10, 105]& // First (* Jean-François Alcover, Feb 13 2013 *)

PROG

(PARI) solve(x=0.6, 0.7, 1-sum(n=1, 60, x^(n*(n+1)/2)))

CROSSREFS

Cf. A023361.

Sequence in context: A058158 A249185 A021159 * A247319 A342359 A140246

Adjacent sequences: A106329 A106330 A106331 * A106333 A106334 A106335

KEYWORD

cons,nonn

AUTHOR

Paul D. Hanna, Apr 29 2005

STATUS

approved